Polymerization of olefins and catalyst therefor



Patented Nov. 7, 1944 PoLYMEnIzA'rIoN F OLEFINS AND CATALYST THEREFORLouis C. Rubin, West Caldwell, N. J., assignor to The Polymerization NoDrawing.

1940, Serial No. 321,5

Pro sey City, N. J., a corpor Original cess Corporation, Jerationof.-Delaware application February 29,

Divided and this application December 16, 1942, Serial No. 469,254 12Claims. (Cl. 260-68315) This invention relates to the conversion ofoleconversion of oleflns to higher boiling hydrocarbon products. Suchpyrophosphates are advantageously employed in the form of granularmasses. The granules may be formed by crushing the filter cake if thepyrophosphate is obtained by precipitation, or by pelleting or extrusionof a more finely divided mixture. Pyrophosphates are employed in thegranular form in orthe conversion treatment must be terminated be-- foreit would be necessary if the granular mass of catalytic material did notbecome softened with resulting collapse and disintegration.

It is an object of the present invention to provide a conversiontreatment wherein the fluid reactants are passed over catalytic contactmaterial, comprising an active pyrophosphate, in the form of granuleswhich are less susceptible to collapse and disintegration than granulesconsisting only of the pyrophosphate. It is a further object of theinvention to provide a method for the conversion of olefinichydrocarbons to hydrocarbons of higher boiling points by thepassage ofsaid hydrocarbons over granular catalytic material which retains itsshape during the conversion operation with the result that operder thatthe fluid reactants may be passed through a granular mass of thecatalytic material at relatively high velocity and without excessivepressure drop.

Each of the pyrophosphates of the metals mentioned above becomes activein the promotion of the conversion reactions by the formation therein,under the conversion conditions employed, of an active modificationwhich is probably the true catalyst for the reaction. Formation of theactive modification probably involves reduction, such as, in the case ofcopper pyrophosphate, reduction of the copper from the cupric to thecuprous state.

It is found that during the conversion treatment the granules becomesoftened whereby they collapse or disintegrate. This is probably due tothe fact that the reactions which result in the formation of the activemodification of the pyrophosphate aflect the material which forms thestructure of the granules. Consequently, during the conversion treatmentthe body of catalytic material employed tends to consolidate graduallywhereby the pressure drop through the conversion chamber is increased.Consolidation of the granular catalytic material through collapse anddisintegration of the granules may result in the accumulation, withinthe body of catalytic material, of relatively high boiling conversionproducts which are less easily removed by the flow of the fluidreactants due to the decrease in the velocity of the reactants in theirpassage through the body of catalytic material. Such deposits decreasethe number of active centers in the catalytic material with the resultthat the conversion rate is decreased. As a result of increase inpressure drop and decrease in conversion rate ating runs of longerduration are made possible but at the same rates of conversion as wouldbe obtained in the presence of a material consisting of an active metalpyrophosphate.

The granular catalytic material employed in the conversion processcomprises a plurality of granules each of which includes a substantialproportion of an active metal pyrophosphate in intimate mixture with afinely divided supporting material which is non-reactive with the metalpyrophosphate, stable under the conversion conditions, and is inert to,or non-reactive with, the modifications, or reduction products, of thepyrophosphate which are formed during the conversion reaction.

The supporting material employed may-be any suitable material which issuitably inert under the conditions of the conversion treatment. Forexample, metal pyrophosphates which are not capable of ready reductionto a polymerization catalyst may be employed as well as metalorthophosphates, such as calcium phosphate in the ortho, pyro, or metaform of the phosphates of tin, nickel, or lead.

Natural materials such as silica, kieselguhr,

alumina, clay, etc. are unsuitable for use as supporting material.

The supporting material is employed in a finely divided form andgenerally should be sumciently sub-divided to pass a 200 mesh screen.For maximum granular strength it is desirable that the supportingmaterial should be employed in a form wherein the particles do notexceed approximately fifty microns in average diameter.

In accordance with the invention the catalytic contact material isemployed in the form of granules which have a volume many times that ofthe granular catalytic individual particles of supporting materialdispersed in each granule. Advantageously, the catalytic contactmaterial is employed in the form of granules having an average diameterof one to ten millimeters although larger or smaller sizes may beemployed as warranted by the character of the reactants and variationsin the reaction conditions. Each granule will therefore have an averagediameter at least ten times the average diameter of the particles ofsupporting material contained therein. Each granule will contain atleast one hundred particles of supporting material and may includethousands of such particles.

Preferably, the desired metal pyrophosphate and the supporting materialare intimately mixed and then pressed into granules of the desired sizeand shape. The granules may be made advantageously by extruding amixture of the sup porting material and metal pyrophosphate in the formof rods of a suitable diameter which are thereafter cut in suitablelengths to form-cylindrical granules of the desired size.

The relative proportions of metal pyrophosphate and finely dividedsupporting material which are employed in the mixture depend upon thedensity of the supporting material. It is found, however, that for eachsupporting material employed there is a preferred range of ratios ofsupporting material to metal pyrophosphate in which are found thecombinations which produce granules of maximum strength and resistanceto softening and disintegration during the conversion treatment.

The mixture of supporting material and metal pyrophosphate is formedadvantageously by maintaining an aqueous suspension ofthe finely dividedsupporting material and efiecting in said suspension a precipitation ofthe desred metal pyrophosphate. In this way at least a portion of themetal pyrophosphate is precipitated on and, possibly, in the particlesof suspended supporting material. The mixture is filtered to obtain afilter cake comprising an intimate mixture of finely divided supportingmaterial and the desired metal pyrophosphate. The resulting mixture maybe broken to form granules of the desired size or may be crushedandpressed or extruded to form pellets of the desired size.

Another method of forming the mixture of pyrophosphate and supportingmaterial involves coprecipitation of the pyrophosphate and thesupporting material. For example, a mixture of copper pyrophosphate andcalcium pyrophosphate may be coprecipitated, the latter being inactiveand serving as the supporting material.

The mixture of active pyrophosphate and supporting material may beformed also by adding the finely divided supporting material to a.slurry of precipitated metal pyrophosphate if adequate precautions aretaken to effect a thorough mixing of the materials.

In preparing the catalytic contact material by methods which involve theprecipitation of the metal pyrophosphate it is desirable in connectionwith certain of the pyrophosphates, particularly copper pyrophosphate,to employ the reagents, such as a soluble pyrophosphate and a solublecopper salt, in proportions such that there is no excess of the solublepyrophosphate over the amount necessary to react with all of the metalsalt present. Preferably, an excess of the metal salt is employed. Thisprecaution is necessary because certain Of the soluble pyrophosphates,such as sodium pyrophosphate, form double salts with copperpyrophosphate and other metal pyrophosphates. The presence of suchdouble salts, during the conversion treatment, appears to retardreduction of the metal pyrophos phates to the active form.

In observing such precaution it is desirable to effect thorough mixingof the soluble pyrophosphate solution and the metal salt solution, andit is advantageous to mix the solutions by pouring the solution of thesoluble pyrophosphate, such as sodium pyrophosphate, into the metal saltsolution whereby there is maintained during the precipitation reactionan excess or the metal salt in relation to the soluble pyrophosphate.Advantageously, the finely divided supporting material is suspended in asolution of the metal salt, such as copper sulphate, and while thesuspension is maintained, for example by stirring, the solublepyrophosphate solution is admixed therewith. Alter continued stirring toinsure adequate mixing of the ingredients the resulting mixture ofprecipitated metal pyrophosphate and supporting material is separatedfrom accompanying water and formed into pellets, as

has been described.

The granular material thus prepared may be used as such'or may haveadmixed therewith granules of inactive material, such as granularcharcoal, the latter acting as a spacer in the contact material.

The invention will be described further by reference to a specificexample wherein copper pyrophosphate is employed as the desired metalpyrophosphate. It is to be understood, however, that such example isintended merely to illustrate the application of the invention and isnot intended to limit the scope of the invention which includes the useof other active metal pyrophosphates and other supporting materials. Theexample furthermore relates particularly to the treatment of normallygaseous hydrocarbon mixtures including gaseous olefins. It is to beunderstood, however, that the invention is not limited to the treatmentof normally gaseous olefinic hydrocarbons but is applicable to thetreatment of normally liquid olefinic hydrocarbons or mixtures of liquidand gaseous olefinic hydrocarbons.

Example Calcium metaphosphate was prepared by heating calcium phosphatemonobasic at 1300 F. for one hour. One part by weight of this material,in finely divided form, was intimately mixed with two parts by weight offinely divided copper pyrophosphate. This mixture was then formed into 15 inch pellets using one per cent graphite. Catalytic material thusprepared was employed in the treatment of a gas consisting, by volume,of 0.3 per cent ethylene, 2.6 per cent ethane, 10.5 per cent propylene,25.4 per cent propane, 10.0 per cent isobutylene, 15.0 per cent normalbutylones and 36.2 per cent butane. The gas, saturated with water vaporat F. and the operating pressure, was passed through the granularcontact mass under a. pressure of 1000 pounds per square inch at a rateof approximately 19 cubic feet (measured as gas at standard conditionsof temperature and pressure) per pound of contact material per hour (orapproximately 1000 volumes of gas per volume of contact material perhour). At a reaction temperature of 425F. the reaction product had aliquid content of approximately 35 per cent. After about ten gallons ofliquid per pound of contact material had been produced the exit gasescontained 6.1 per cent -with lower percentages of water.

unsaturates, representing 88 per cent conversion. After about 30 gallonsof liquid per pound of contact material had been produced the exit gasescontained 10.0 per cent unsaturates, representing 79 per centconversion, the gas charge having been changed meanwhile to oneconsisting of, by volume, 0.5 per cent ethane, 9.0 per cent propylene,22.4 per cent propane, 10.6 per cent isobutylene, 16.3 per cent normalbutylenes, and 41.2 per cent butane. The run was terminated after 296hours and a liquid production of over 33 gallons per pound of contactmaterial. of the contact material was recovered in granular form. I

It is found that in the preparation of the cata- The greater part lyst,as in the foregoing example, the mixture;

prior to extrusion, should be dried to a water content of not more than60 per cent and not less than 40 per cent in order to produce pellets ofsufiicient strength. In general it is noted that the apparent density ofthe dried pellets is a direct function of the water content of theextruded mixture, higher density being associated The mechanicalstrength of the pellets is improved with increasing apparent density.

In carrying out the process of the invention as illustrated by theforegoing example the gases'or other hydrocarbon fluid are passed incontact with the catalytic contact material in a suitable chamber orreactor, the gases being suitably preheated. Any suitable pressure maybe used, but it is preferable to employ relatively high pressures, forexample inexcess of 150 pounds per square inch, although atmosphericpressure or lower pressures may be employed. The rate of polymerizationof the olefinic hydrocarbons is a function of the concentration of thesematerials, and accordingly for maximum conversion such reactions arebest run at superatmospheric pressure. The use of relatively highpressures apparently also has a beneficial effect on the granularcontact material in assisting to preserve its original form whereby runsof longer duration are possible.

The optimum reaction temperature depends somewhat upon the nature of thematerial under treatment and the product desired. For example,conversion of gaseous olefins such as butylenes at a temperature ofapproximately 300 to 400 F. is advantageous for efiecting maximumconversion to a product consisting essentially of gasoline constituents.In the treatment of a gaseous mixture containing substantial quantitiesof propylene, as in the foregoing example, a temperature of 400 F. orhigher is desirable for effecting substantial conversion.

The extent of reaction and the character of the liquid product areafiected also by the length of reaction time during which the chargeremains in contact with the contact material under the operatingconditions. In general the hydrocarbons should be passed over thecontact material at a rate of 2 to 50 cubic feet (measured as gas atstandard conditions of temperature and pressure) per pound of catalystper hour. Otherwise expressed, the hydrocarbon fluid may be passedthrough the reactor at a rate of 50 to 6000 volumes per hour per volumeof catalytic contact material depending upon the apparent density of thecontact material. For material having an apparent density of about 0.5this range would be 60 to 1500 volumes of contact material per hour.

It is apparent that for any given charge the I extent of reactiori andthe character of the liquid j; product depend mainly upon the operatingpres sure, the operating temperature and the space velocity of thecharge. Many combinations of these variables will yield the desiredamount and quality of product. For example, in the treatment of agaseous mixture containing substantial quantitie o isobutylene it may bedesirable to operate ata re atively low temperature or with relativelygreat space velocity, or both, in order to limit the extent ofconversion whereby the product consists largely of the polymers ofisobutylene. Within the range of operating temperatures preferred in thepresent process (300 to 600 F.) isobutylene is more readily polymerizedthan normal butylene or propylene whereby selective polymerization maybe efiected by limiting the extent of conversion as described. Naturallymore complete conversion may be effected by raising the temperature orreducing the space velocity, or both.

The moisture content of the reaction mixture apparently has no directeffect on the reaction. However, a saturated charge apparently has aslight beneficial efiect in maintaining the original condition of thecontact material. In any event, therefore, there is no necessity forcomplete drying of the charge to the process.

This application is a division of application Serial No. 321,521, filedFebruary 29, 1940, by Edwin T. Layng and Louis C. Rubin which issued asPatent No. 2,310,161, on February 2, 1943, to Edwin T. Layng.

I claim:

1. The method of converting olefinic hydrocarbons to hydrocarbons ofhigher boiling points which comprises contacting said olefinichydrocarbons at elevated temperature with a catalytic contact materialcomprising an intimate mixture of at least one metal pyrophosphatecapable of reduction to a polymerization catalyst as the essentialactive ingredient of said contact material and a metal phosphate notcapable of ready reduction to a polymerization catalyst.

2. The method of claim 1 wherein said metal pyrophosphate capable ofreduction to a poly merization catalyst is selected from the groupconsisting of pyrophosphates of copper, mercury, zinc, magnesium, iron,aluminum and cobalt.

3. The method of claim 1 wherein said metal pyrophosphate capable ofreduction to a polymerization catalyst is copper pyrophosphate.

4. The methood of claim 1 wherein said metal pyrophosphate capable ofreduction to a polymerization catalyst is mercury pyrophosphate.

5. The method of claim 1 wherein said metal pyrophosphate capable ofreduction to a polymerization catalyst is cobalt pyrophosphate.

6. The method of claim 1 wherein said metal phosphate not capable ofready reduction to a polymerization catalyst is a calcium phosphate.

7. The method of converting olefinic hydrocarbons to hydrocarbons ofhigher boiling points which comprises contacting said olefinichydrocarbons at elevated temperature with a catalytic contact materialcomprising a granular mass wherein each granule consists of a mixture ofat least one metal pyrophosphate capable of reduction to apolymerization catalyst as the essential active ingredient of saidcontact material and a metal phosphate not capable of reduction to apolymerization catalyst.

8. Catalytic contact material for promoting the polymerization ofolefinic hydrocarbons comprising a mixture of at least one metalpyrophosphate capable of reduction to a polymerization catalyst as theessential active ingredient of said contact material and a metalphosphate not capable of ready reduction to a polymerization catalyst.

9. Catalytic contact material for promoting the polymerization ofolefinic hydrocarbons comprising a plurality of granules each consistingof an intimate mixture of at least one metal pyrophosphate as theessential active ingredient of said contact material and a metalpyrophosphate not capable of ready reduction to a polymerizationcatalyst.

11. Catalytic contact material for promoting the polymerization ofoleiinic hydrocarbons comprising an intimate mixture of at least onemetal pyrophosphate capable of reduction to a polymerization catalyst asthe essential active ingredient of said contact material and a calciumphosphate.

12. Catalytic contact material for promoting the conversion of olefinichydrocarbons consisting of an intimate mixture of copper pyrophosphateas the essential active ingredient of said contact material and acalcium phosphate.

LOUIS C. RUBIN.

